Engineered nanomaterials (ENMs) have an unknown toxic potential and the relationship between the biological effects and the physicochemical properties remains uncertain. Our long-term research goal is to enable an efficient and accurate safety profiling of ENM of varying characteristics and conditions of exposure that would enhance decision-making regarding human exposure risks. Our objective in this application is to determine serum compositional changes resulting from pulmonary ENM exposure that lead to systemic toxicity (vascular and neural, primarily). We propose the following specific aims, which will pair innovative ex vivo bioactivity outputs with advanced high-resolution mass spec compositional analysis. In the first Aim, we will ascertain mechanisms of pulmonary origin of modified circulatory components related to metalloproteinase activity and inflammation. Evidence suggests that circulating factors may be related to a) direct reactions of ENMs and pulmonary cellular/molecular components or b) degradation by-products of increased metalloproteinase activity and that the circulating components act through endothelial cell surface pattern recognition receptors. In the second Aim, we will assess neurovascular and central nervous system impacts arising from pulmonary ENM- induced serome modifications. Here, we will develop and optimize a sequence tag-based algorithm to enhance the identification of endogenous peptides within the multi-walled carbon nanotube (MWCNT)-responsive serome, which will facilitate evaluation of the ENM-induced bioactivation in the cerebrovasculature and the diffusivity of ENM-responsive serome factors across the blood brain barrier. Lastly, in the third Aim, we will assess MWCNT-associated circulatory characteristics and inflammatory potential in samples derived from an occupationally-exposed cohort. We will assess the serum bioactivity in terms of endothelial activation and link to personal breathing zone measurements of elemental carbon, a marker of carbon nanotube/nanofiber exposure. At the completion of this project, we expect to have identified key physiological and chemical factors that influence plasma-borne ENM toxicity. The successful completion of these studies is expected to constitute an important step towards preventing / attenuating adverse health effects associated with ENM exposure. An added benefit will be the generation of novel diagnostic technologies and biomarkers that can not only strengthen, but also expedite ENM safety assessments and exposure monitoring. The research results will directly address Strategic Goals 1, 2, and 4 of the 2013-2016 NIOSH Nanotechnology Research and Guidance Strategic Plan.